Measured-service telephone system



Aug. 10,1926. 1,595,095

V. E. HOFFMAN v MEASURED SERVICE TELEPHONE svs'mu Filed Dec. 50, 19 2 2Shea s-shut 1 I l Q {d k //z A. i

Im.ren ur+- v Unc EHnJTman Aug. 10 1926. 1,595,095

v. E. HOFFMAN MEASURED SERVICE TELEPHONE SXSTEM Filed Dec. 30, 1922 2Sheets-Sheet 2 4Z2 Eff- Patented Aug. 10, 1926.

UNITED STATES VANCE E. HOFFMAN, OE CI-IICAGQ'ILLINOIS, ASSIGNOR, BYMESNE ASSIGNMENTS, TO

AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA-wnnn.

'MEAsunEn-snnvmn TELEPHONE SYSTEM.

Application filed December 30, 1922. Serial No. 609,855.

The present invention relates in general to measured servicetelephonesystems, but

is more particularly concerned with systems i of this character in whichautomatic switches are used for connecting calling and called lines; andthe object of the invention is the provision of new and useful metercontrolling equipment and circuits which are adapted for use incontrolling the operation of meters to assess variable charges.depending upon class of the line calling, the particular connectionestablished, and the time the talking connection is maintained.

Other minor features of the invention will be pointed out in thedetailed description and claims which follow.

Referring to the drawings, Figs. 1 and 2 are circuit diagrams which showonly a portion of the apparatus required to complete a connectionbetween a calling and a called subscriber; but in view of the Well knowncharacter of the apparatus, and of the fact that telephone systems ofthis character are now well understood, it is believed that suficienthas been shown to enable the inven tion to be readily understood. Figs.1 and 2 show how Figs. 1 and 2 may be slightly modified where conditionsare different, as will subsequently be. explained.

In Fig. 1, the substation indicated by reference character A is anordinary automatic substation which comprises the usual talkingequipment and ringer, and also a calling device S, through the medium ofwhich the subscriber controls the central office switches.

The line conductors 1 1 and 12 ext-end to the exchange where theyterminate in the rotary line switch G, which may be briefly described asa line switch whose wipers have a rotary movement in a forward directiononly, and which have no normal position, 'that is, 'when the switch isreleased the wipers do not return to normal but remain on the set ofcontacts last used. A plurality of these individual line switches may begiven access to a group of trunk lines extending to first selectorswitches, and one of the trunk lines to which the line switch C hasaccess is shown in the drawing as extending to the first selector D. Theselector D is vertical and rotary switch of familiar construction, andtogether with a plurality of similar selectors, has access to aplurality of groups of trunk lines.

In the drawing I have shown two sets of contacts in the first and secondlevels of the selector D. but it is understood that the selectors willhave ten levels corresponding to ten diiferent groups of-trunk' lines.'One of the trunk lines terminating in the first level is the trunk linecomprising conductors 7780, inclusive, which extends to the repeater B(Fig. 2) and then continues by way of conductors 200 and 201,- to adistant exchange, where the conductors 200 and 201 terminate in the linerelay of a second selector switch. The repeater R has the usual functlonof a repeater in a two-wire 'automatictelephone system, but has beenmodified to performadditional functions which will be pointed outshortly. j

The relays, such as 51, for example, which have their lower portionsshaded are of the type which are relatively quick to pull up, but whichare .slow'to release, whereas relays, such as 14 of the line switch C,which have their cores partly shown in solid black are of the type whichare both slowto pull up and slow to fallback.

In the system contemplated herein, the

exchange to which the trunk line comprising conductors 200 and 201extends is a switching center or distributing point for a num ber ofother exchanges, and includes second and third selectors (in some casesthe third selectors may be in a third exchange) by means of which callsare routed to the exchanges'in which the called lines are located. Itwill be evident, then, that after a call has been extended as far as therepeater R, two more digits must be called before the exchange to whichthe call is going is definitely determined, and since the charge for thecall is to be'in accordance with the terminating exchange, some meansmust be provided for registering" the second and third digits in orderthat the proper charge can be assessed. This means comprises the switchS, which is individual to the repeater R. The switch S is a vertical androtary switch having 100 contacts arranged in rows or levels and a wiper130 for engaging such contacts.

Now since the'meter used is of the type usuallyused in counting thenumber of co1npleted outgoing calls, and further since in the presentcase it is required to register the actual time during whichconversation takes place, it is necessary to provide means forperiodically operating it at a speed determined by the amount which isto be charged per time unit for the particular connection established,and in some instances, upon the class to which the calling subscriberbelongs.

In the present case the means for periodicomplish this result it hasbeen provided with a permanent magnet 152, which provides a means forinsuring both a quick make and a quick break of the contacts.

In order to make clear just how the magnet is made to accomplish thisresult the op eration of the thermostat may be briefly described asfollows: The thermostat bar normally rests against the contact screws156 and 154 with considerable tension, which the magnet 152, pulling onthe pole piece 155, is unable to overcome. l/Vhen the winding isenergized, however, and the bar begins to heat up, this tension isgradually reduced, for the compound bar tends to curve downwardlybecause of the unequal expansion of its two parts. At a certaintemperature the tension of the bar against its contacts becomes reducedto a POIIIL where it can no longer withstand the pull of the magnet,whereupon the bar is quickly pulled down until residual screw 151engages the pole of the magnet. This operation breaks the circuitthrough the thermostat winding and the bar begins to cool oft. It isheld by the magnet, however, until the cooling process has proceeded toa considerable extent, because the pole piece 155 is now relativelyclose to the magnet pole and is strongly attracted. Eventually the barcools enough so that the magnet can no longer hold it and it flies backto its initial position, making firm contact again against the contactscrews 156 and 154. The initial tension is adjusted by means of screw150 and the point at which the bar is released by magnet 152 is adjustedby means of brass residual screw 151, from which it will be understoodthat the operation can be adjusted over a wide range of temperatures,while the rate can be varied to a considerable extent tor any giventemperature.

Having described in a general way the apparatus shown herein, I willnowdescribe the operations which take place during the establishment of theconnection. It will be assumed, for example, that the subscriber atsubstation A desires to connect with a subscriber in a distant exchangeaccessi lo by way of the exchange to which the trunk line comprisingconductors 200 and 201 ere tends. Vfhen the receiv r is removed atsubstation A, a circuit is completed over the line conductors 11 and 12for the line relay 1% of the line switch C. Upon energizing, the linerelay 1% completes a circuit extend ing through the switching relay 13the stepping magnet 21 in series to battery. This circuit is completedat armature- 20 of the line relay, and at armature 19 the test wiper 32is connected to tie above circuit at a point midway between theswitching relay and said stepping magnet. The operation now depends uponwhether the test contact with wiich the test wiper 32 is in engagementis busy or not busy. If this test contact is busy, it will lave agroundpotential upon it, the switching relay 13 will be short circuited andthe stepping magnet 21, which interrupts its own circuit, will beoperated in the manner of a buzz-r to advance the switch wipers 30-33,inclusive, step by step in search of an idle trunk line, This operationwill continue as long as the test wiper 32 continues to engage groundedor busy test contacts. However, we may assume that in the present case,when the call is initiated, the selector D is idle, and the test contact36 therefore is not grounded. In these circumstances, when the linerelay 14 is energized, the switch: relay 13 is energized immediatelyafter wards, with the result that the line conduc tors 11 and 12 aredisconnected from the line relay 1 1 and from ground, respectiwly, andare extended by way of armatures 15 and 18 and their working contacts,line wipers 30 and 33, trunk conductors 38 and -10, and armatures 60 and63 and their resting contacts to the upper and lower windings,respectively, of the line relay 50 of the selector D.

Upon the extension of the calling line as above described, the linerelay 50 will be energized over the line circuit and will clesev acircuit for the slow acting release relay 51. Upon energizing, relay 51prepares the selector D for vertical operation in the usual manner, andalso completes a holding circuit extending back to the line switch r)over the following path: grounded wo ing contact of armature 6 1 andsaid arma ture, conductor 39, test contact 36., test wiper 32, armature17 and its working centact, winding 01" switching relay '13, and thewinding of the stepping magnet 21 to bat tery. It is understood that theabove circuit is established before the slow acting rclay 14; has hadtime to deenergize.

The calling subscriber may now operate his calling device in accordancewith the first digit of the desired number. A series of'interruptions isthereby produced in the circuit of line relay 50, causing acorresponding series of deenergizations of the said relay which at eachdeenergization sends a current impulse through the slow acting relay 52and the vertical magnet 56 to battery. By the operation of the verticalmagnet 56, the switch shaft is raised step by step until the wipers69-72, inclusive, stand opposite the bank level in which are terminatedthe trunk lines leading to the desired exchange. In the present case,the wipers will be raised opposite the level containing bank contacts7346, inclusive. The slow acting relay 52 is energized in series withthe vertical magnet, retaining its armatur, attracted throughout thevertical movement of the switch, and upon the closure of off normalcontact springs 58, completes a circuit for the stepping relay 53. Uponenergizing, relay 53 establishes a locking circuit for itself at itsupper armature, and at the lower armature prepares a circuit for therotary magnet 54. At the end ofthe vertical movement of the switch theslow acting relay 52 is deenergized and closes the circuit of the rotarymagnet, which is thereupon energized to rotate the switch wipers intoengagement with the first set of bank contacts in the level oppositewhich they were raised. The rotary magnet also breaks the lockingcircuit of the stepping relay 53, which, accordingly, is deenergized tobreak the circuit of the rotary magnet, which thereupon ceenergizesalso, and again closes its interrupter contacts. The operation nowdepends upon whether the test contact with which the test wiper 71 is inengagement is busy or is not busy. If this test contact is busy it willhave a ground potential upon it, and the stepping relay 53 will again beenergized over a circuit which extends from the grounded test contact byway of the test wiper 71, armature 61 and its resting contact, offnormal springs 58, interrupter contact'of the rotary magnet 5 1-, andthe winding of the stepping relay 53 to battery. The stepping relaywill, therefore, again close the circuit of the rotary magnet, whichwill operate to advance the switch wipers into engagement with the nextset of bank contacts. This operation in which the stepping relay 53andthe rotary magnet 54 are alternately energized and deenergized takesplace very rapidly, and will continue as long as the test wiper 71continuesto engage busy or grounded test contacts. In the present case,it will be assumed that the trunk line shown in the drawing is the firstidle. trunk line, and when, therefore, the test wiper 71 arrives at testcontact 7 1 and the rotary magnet 5% is deenergized, the stepping relay555 will not a ain be ener izedz but the switching relay 55, whichheretofore has been short circuited, will be energized by current flowover the following path: grounded conductor 89, winding of switchingrelay 55, oil normal springs 58, interrupter contacts of the magnet 54;and the winding of the stepping relay 53 to battery. Owing to the highresistance of the switching relay 55, the stepping relay 53 is notenergized by current flow in the above circuit. Upon energizing, relay55 disconnects the trunk conductors 38 and 40 from the windings of theline relay 50 and extends them by way of armatures and 63 and theirworking contacts, line wipers and 72, bank contacts 73 and 75,conductors 80 and 78, and normally closed contacts of reversing relay100, to the upper and lower windings, respectively, of the double woundline relay 101 of the repeater R.

The line relay 101 is accordingly energized over the line circuit, and,upon attracting its armature 110, completes a circuit for the slowacting release relay102. Upon energizing, relay 102 at its armature 113,closes circuits through the polarizing winding of the electro-polarizedrelay 104 and slow acting relay 105, at its armature 112 preparesoperating circuits for slow relays 103, 125, and vertical magnet 124:,which circuits will be later described, and at its armature 11 1completes a holding circuit extending back to the selector D over thefollowing path: grounded resting contact of armature 1 13 and the saidarmature, armature 123 and its working contact, working contact ofarmature 11 1 and the said armature, conductor 77, test contact 74, testwiper 71, and armature 61 and its working contact to the conductor 89,where it joins the previously described holding circuit extending backto the line switch C. The circuit just described serves to maintainrelays 55 and 13 energized throughout the connection. As a furtherresult of its energization, relay 102 closesv a bridge across the trunkconductors 200 and 201 which may be traced as follows: conductor 200,working contact of armature 115 and the said armature, armature 116 andits resting contact, upper winding of electropolarized relay 104:,normally closed contacts controlled by armature 109, right hand windingof impedance coil 107, and armature'133 of the now energized line relay101 and its working contact to the trunk conductor 201. By the closureof the bridge just described, a circuit is completed for the line relayof the second selector in the distant exchange (not shown) in the usualman ner, and the said line relay and its associated slow acting releaserelay are accordingly energized and the distantselector is prepared foroperation.

The calling subscriber may now operate nezzt digit in the desirednumber, thereby causing a series of deenergizations of the line relay101 of the repeater R, which at each deenergization, opens the bridgeacross 'DhQ-tIUIllI conductors 200 and 201 and thereby interrupts thecircuit of the line relay of the distant selector switch. The saidselector is accordingly operated in the well known manner to raise itswipers in accordance with the digit called, after which the said wipersare rotated and connection is established with an idle trunk lineextending to another selector switch. At the repeater R, while the linerelay 101 is deenergizing intermittently to repeat impulses to thesecond selector switch in the distant exchange, it sends an impulse ateach deenergization from grounded armature 110 and its resting contact,armature 112 and its w rking contact, to point 140 where the circuitdivides, one branch extending to the winding of slow acting relay 103 tobattery, and the other branch extending through armature 122 and itsresting contact, off normal springs 137 and 139, winding of slow actingrelay 125, and the winding of vertical magnet 124 to battery. The relays103, 125, and magnet 124 are energized upon the first impulse, and therelays 108 and 125 being of the slow acting type, remain energizedthroughout the series of impulses. The relay 103, in operating,completes the bridge across trunk conductors 200 and 201 over anon-inductive path which may be traced from trunk conductor 200 by wayof armature 115 and its working contact, armature 116 and its workingcontact, and armature 133 and its working contact to the trunk conductor201. This operation, by re moving the windings of relay 104 andimpedance coil 107 from the circuit, produces a better control circuitfor operating the series of switches in the distant exchange. Theoperation of relay 125 prepares a new circuit for itself which iscompleted upon the first vertical movement of the switch, which causesthe operating circuit for relay 125 and magnet 124 to be switched overtocontacts 137 and 138 of the off normal switch in well known manner.The vertical magnet 124 responds to each impulse of the series toposition the wiper 130 opposite a desired level of its bank contacts,such as the level containing contact 136. At the end of the series ofimpulses, the slow acting relay 125 deenergizes and in so doing,switches the operating circuit trom the vertical magnet 12-4 to the rotmagnet 127.

The calling subscriber may now call the third digit of the callednumber, with the result that another series of interruptions is producedin the circuit of line relay 101, which repeats impulses to the nextselector of the series to effect selection of a trunk line leading tothe exchange in which the called subscriber is located- At the sametime, the line relay also repeats impulses over the previously pointedout path to the slow relay 120 and rotary magnet 127 of the switch S,causing its wiper 130 to be positioned on a bank contact, which contactis connected through a resistance to ground. At the end of the series ofimpulses, the slow relay 126 deenergizes, completing a circuit fromground, resistance 144, 140, or 141, depending, of course, on the seriesof impulses which positioned the switch S, to relay 106. Assuming thewiper 130 to be on bank contact 136, the circuit will'be completed fromground, resistance 144, bank contact 136, wiper 130, resting contact ofarmature 134 and the said armature,normally closed contacts controlledby armature 120, and the winding of relay 106 to battery- Relay 106, inoperating, opens the operating circuit of the rotary magnet 127 at itsarmature 122, at its armature 120 completes a holding circuit foritself, and at armature 121 connects the wiper 130 with the conductor163.

The calling subscriber may now call the remaining digits in the desirednumber, with the result that additional series of interruptions areproduced in the circuit of the line relay 101, which operates as beforeto repeat the interruptions, and thereby brings about the operation ofthe switches in the terminating exchange which are required to completethe connect-ion with the called subscribers line. The bell at the calledstation is thereafter rung automatically, and when the called subscriberremoves his receiver responsive thereto, the ringing equipment isautomatically out 011, and the called station is supplied with talkingbattery through the windings of the back bridge relay of the connectorin the usual manner. As is customary, this back bridge relay is providedwith contact springs which reverse the connections of the incoming lineconductors, thereby reversing the direction of current flow overconductors 200 and 201, and through the upper winding of theelectro-polarized relay 104 at the repeater B. As a result, the relay104, which heretofore has remained inoperative, is operated, and at itsarmature 118 closes a circuit through Belay 100. Relay 100 is areversing relay which reverses the direction of current flow in theincoming trunk conductors 76 and 78, for no useful purpose, however, inconnection with the apparatus shown; but inasmuch as it is a standardoperation and is of utility under certain circumstances which it willnot be necessary to mention, the circuits have been shown in thismanner. Relay 100 also connects at its armature 109 the left handwinding of the impedance coil 107 in series with the right hand winding,with the object of increasing the efficiency of the talking circuit, atits armature 143 removes relay 42 looks itself up over the release trunkconductor in an obvious manner, and .at its armature 11 completes themeter operating circuit which may be traced as follows: from ground,resistance 14: 1, bank contact 136, wiper 130, resting contact ofarmature 13 1 and the said armature, working contact of armature 121 andthe said armature, conductor 163, through the break contacts and windingof the thermostat T, conductor 7 9, bank contact 76, wiper 69, workingcontact of armature 41 .and the said armature, working contact ofarmature 16 and the said armature, Winding ot' meter magnet M to battery and ground.

The precise manner in which the metering operation take place will nowbe described. WVhen the metering circuit is closed, the call meter M isoperated and is reoperated periodically thereafter at a rate determinedby the amount of current flowing through the thermostat. This currenvalue is dependent upon the resistance included in the circuit by thepositioning of wiper 130, which as has been previously described ispositioned in accordance with certain digits oi the called number, andupon the class of the line calling. 7 1 1 {I5 The meter circuit and thecircuit for the thermostat having been closed upon the called partyanswering will remain closed until the thermostat has heated upsufficiently to have its normal tension overcome by the magnet, at whichtime the circuit is interrupted, the meter magnet restores its armaturein preparation for the next impulse, and the thermostat begins to cooloff. As soon as it has cooled to a predetermined degree it releasesitself from the influence of the magnet and again completes the meterand thermostat operating circuits. This operationis repeated throughoutthe period of conversation.

Since the line calling is not a party line it is provided with theresistance 9 connected in multiple with the meter winding which permitsa maximum amount of current to flow through the thermostat winding. Thiscauses the thermostat to heat up quickly, and therefore the meter isoperated at the maximum speed.

Attention is called to the fact that while only two bank levels of theswitch S have been shown, it is to be understood that in practice therewill be the usual ten' levels. Furthermore, while one level isillustrated as having the same resistance associated with all bankcontacts, it is to be understood that the resistance associated witheach contact in the bank may be or a dilierent value, thus giving thethermostat T a wide selection or operating circuits in accordance withany of 100 exchanges to which the calling subscriber may have access.

When the conversation is finished, both subscribers will hang up theirreceivers. When the receiver is replaced at substation A, all theswitches involved in the con nection are released and restored tonormal, the release being initiated by relay 101 of the repeater R, Upondeenergizing, relay 101 opens the bridge across the trunk conductors 200and 201, which causes the switches in the distant exchange to release inthe usual. manner. The slow acting release relay 102 is also deenergizedfollowing the deenergization of relay 101, and breaks the holdingcircuit extending back over conductor 77 to the selector 1) and lineswitch 0.

As a result, relays 55 and 13 are deenergized and the said switches arerestored to normal in the usual and well known manner. The relay 102 atits armature 112 and its resting contact also completes a circuit forthe release magnet 125 of the switch S, causing the same to restore inwell known manner.

All equipment has now restored to normal,

to party line subscribers, their rates are 're duced below those of thestraight line sub scribers, the amount of reduction depending on thenumber of subscribers on the party line. The straight line meters (asshown) are-shunted by a resistance 9 which as previously describedpermits an additional amount of current to flow through the thermostat,causing the meter to be operated at a maximum speed. Now in equippingthe two party line meters a higher resistance may be used, while in thecase of the four party lines the resistance may be omitted, thusproviding for three diflerent charging rates corresponding tothe threegrades of service mentioned. In case a subscriber uses 7 differentgrades of service to which the subscribers are entitled as well as inaccordance with the destination of the calls.

Party line meters suitable for use in the same system with theindividual line meter shown, and controllable without charge by thecircuits illustrated herein, are describedin Patent No. 1,486,900,issued to Emil J acobsen, March 18, 1924'. V

In cases where all calling lines are of the same class, or where it isdesired that the meters be operated at the same rate regardless ofwhether the line in use is a party or straight line, the meter controlcircuits may be readily modified in such a manner that a local operatingcircuit is provided for the meter This permits a greater variation ofthe resistance values used in the bank contacts of the switch S,permitting a greater maximum value o t current to flow, and a resultantgreater range in the rate of operation of the thermostat. This isespecially desirable if the exchanges or offices are widely separated.To modify the circuits it is only necessary to connect the conductor 79to conductor 16% instead of to the thermostat winding, and to connectthe thermostat winding to spring .160 of relay 100 as illustrated in.Fig. 2 Now when relay 100 becomes energized it permits the operation ofthe relay 4-2 of the selector D in the same manner as previouslydescribed to complete the local operating circuit for the meter M, andin addition closes. an operating circuit for the thermostat at itsarmature 162.

l/Vhile this application illustrates the invention as ,used in a systemwherein there are a large number of ofiices, it may equally well beapplied to a system having ten or even a smaller number of oilices. Insuch a system the switch S, and relay 106 may be entirely dispensedwith, in which case the thermostat will be inserted in the meterconductor of the selector D as illustrated in Fig. 1 Each level of bankcontact-s such as 76 of the selector will have all its contacts tiedtogether, and the whole will be connected to a resistance value inaccordance with the rateof charge to be made for connection to theexchange reached over that level. Oi course as is well known the switchD having ten levels permits the connection of ten different resistancevalues in accord ance with difierent rates to be charged for connectionswith the ten exchanges in the system.

Having described the invention, what is to be considered new and desiredto have protected by Letters Patent will be pointed out in the appendedclaims. I

What I claim is: w 1. In a telephone system, calling lines of differentclasses independent or" their location, meters for said lines, aplurality of exchanges, a trunk line accessible to said calling linesfor extending connections to called lines in any of said exchanges,means for completing a. meter operating circuit for the calling linewhen a connection has been es tablished, and means operative tointerrupt said circuit periodically at a rate dependent jointly upon theexchange in which the pan ticular station called is located and upon theclass of the line calling.

2. In a telephone system, a line, a meter for said line, automaticswitches for extending connections from said line to called lines, saidswitches responsive to series of impulses transmitted over the saidline, meansoperated by certain of said series of impulses fordetermining the amount of current which will be permitted to flowthrough said meter at any period when a talking connection has beenestablished, and thermostatic device included in the meter circuitoperative to periodically open and close said circuit at intervalsdependent on the amountof current flowing.

3. in a telephone system, a line, a meter -for said line, a trunk line,automatic switches for extending connections over said t Link from saidfirst line to called line-s, means op= erable when a call is answeredfor causing a flow of current through said meter, and means operated inresponse to such current flow for periodically interrupting the currentflow through said meter while the con nection is maintained.

4;. In a telephone system, a calling line, a meter for .aid line, atrunk line, automatic switches for extending a connection over saidtrunk from said calling line to a called line, means operable when thecall is answered to cause a current fl w through said meter, m ansassociated with said. trunk for determining the current tlow inaccordance with the location of the called line, and means op crable toperiodically interrupt the current flow in said meter at a ratedependent on the amount of current flowing therethrough.

5. In a telephone system, a line, a meter for said line, trunk lines,automatic switches for extending the line over said trunk lines tocalled lines, another switch operable simultaneously with certain ofsaid automatic switches for selecting an operating circuit for saidmeter, and means included in the selected operating ircui-t and operatedby the current flowing therein, for period ically interrupting the sameat a rate determined by the operating circuit selected,

6. In a measured service telephone system in which the subscribers aregraded according to the class of service to whic h'they are entitled,automatic means for always assess ing charges against calling l-ines ata rate depending on the particular connection set up, and meansassociated with other classes of calling lines for changing theopeiating rate of said last means in all connections set up inaccordance with the grade of service the subscriber calling is entitledto.

7 In a measured service telephone system in which the subscribers aregraded according to service furnished, automatic means for assessing varing char es against a callu v D O ing line depending on the grade ofservice the subscriber is entitled to, the distance from the calling tothe called subscriber, and the duration of conversation.

8. In a measured service telephone system in which the subscribers aregraded according to service furnished, automatic means "for assessingcharges against a calling line depending on the grade of service thesubscriber is entitled to, the location of: the called subscriber andthe location of the call ing subscriber.

9. In a measured service telephone system in which the lines areprovided with meters, circuits for said meters, a heat operatedinterrupter device included in said circuit with the meter of a callingline to operate the same periodically.

10. In a measured service telephone systemin which the subscribersaregraded according to service furnished, a heat operated device forassessing charges against a calling line in accordance with the grade ofservice to which the subscriber is entitled.

11. In a measured service telephone system in which the lines areprovided with meters, said system comprising means for closing the metercircuit or" a calling line when the called subscriber answers, and athermostatic device included in said meter circuit to interrupt the sameperiodically.

12. In a measured service telephone system in which the lines areprovided with meters, said system comprising means for closing the metercircuit of a calling line when the called subscriber answers, means ,IOIvarying the resistance of said circuit in accordance wlth the locatlonof the called line, and a thermostatic device in said circuit operableto interrupt the same at a rate proportionate to its resistance.

13. In a telephone system, a pair of calling lines, a meter for eachline, a meter controlling device common to said meters, said deviceoperated to interrupt the circuit of the meter with which it isassociated to assess charges thereon, and means associated with one ofsaid meters for causing said device to operate at difi'erent rate ofspeed.

I l. In a telephone system, subscribers lines arranged in two diilerentclasses, a high rate and a low rate class, means for extendingconnections from said lines, means for automatically assessing varyingcharges on calling line dependent upon the value of the extendedconnection, and additional means for varying said charges when thecalling line is of the high rate class.

15. In a measured service telephone system, subscribers lines, certainof said lines arranged to be charged at a lower rate than other linesregardless of the line called, and automatic means for assessing chargesagainst a line of either class in accordance with the value 01": theconnection extended therefrom.

16. In a measured service telephone sys tem, a plurality of callinglines of different classes, meters for said lines, a meter controllingdevice common to said lines, means for setting up connections from anycalling line to a called line, means for causing said meter controllingdevice to operate at a speed dependent on the line called, and meansassociated with the meter of acertain one of said lines for causing themeter controlling device to operate at a different rate.

17. In a measured service telephone system, lines, meters for saidlines, a meter controlling device common to said lines, means forsetting up connections to called lines,

means for causing said meter controlling device to operate the meter ofa line calling at a rate dependent on the line called, and meansassociated with the meters of certain lines for altering the rate ofoperation of said meter controlling device regardless of the linecalled.

In witness whereof, I hereunto subscribe my name this 26th day ofDecember, A. D., 1922.

VANCE E. HOFFMAN.

